Larsen, R. J. and Falk, D. E. 2013. Effects of a seed treatment with a neonicotinoid insecticide on germination and freezing tolerance of spring wheat seedlings. Can. J. Plant Sci. 93: 535-540. Spring wheat is a major crop in Canada, and in the western and northern regions of the production area early planting is required to ensure high yield, and high grain quality. This puts the crop at risk for exposure to early season cold or freezing temperatures. This study examined whether germination and freezing tolerance of seedlings of 11 spring wheat cultivars is affected by a seed treatment containing a neonicotinoid insecticide. As a result of the seed treatment, the number of germinating seeds was significantly higher for treated than untreated seed lots. There was also a slight (5.7%), but significant increase in freezing tolerance of treated plants based on the vigour of regrowth of seedlings exposed to -4°C in controlled freezing tests performed indoors. Differences in the response to the neonicotinoid insecticide treatment were observed between varieties. These preliminary results indicate that the seed treatment may be effective in improving germination and freezing tolerance of spring wheat as assessed in indoor screening tests. Further testing will be required to establish whether a positive effect can be confirmed in more variable outdoor environments and in other cereal crop types.